1. Field of the Invention
The present invention relates to an all terrain vehicle for running on uneven ground such as wasteland, grassland and swamps. More particularly, the present invention relates to technology for a vehicle body frame.
2. Description of the Related Art
An all terrain vehicle with an independent suspension for each of the left and right rear wheels is generally provided with a vehicle body frame including left and right suspension arm support portions at a rear portion of the vehicle. Left and right suspension arms that are capable of moving up and down are respectively connected to the left and right suspension arm support portions. The rear wheels are supported at the tip end of these suspension arms (refer to U.S. Pat. No. 6,805,217).
FIG. 7 is a plan view of a vehicle body frame provided in a conventional all terrain vehicle. As shown in FIG. 7, left and right suspension arm support portions 101 are parallel to each other. Therefore, it is easier to connect other parts of the vehicle to the suspension arms 102.
However, in the vehicle body frame 100 including these types of parallel suspension arm support portions 101, there is a desire to shorten the frame rear portion and make the vehicle more compact. Specifically, since the center portions 103 of the vehicle body frame support an engine 104 etc., a distance between the left and right portions 103 is wide. At a position toward the back from the central portions 103, left and right vehicle body frames 100 respectively include two bent portions. More specifically, each of the vehicle body frames 100 is bent inwardly in a vehicle width direction at a rear end portion 103a of the central portion 103. Inclined portions 105 extending from these rear end portions 103a extend backward and inward (to the center in the vehicle width direction). Then, each of the vehicle body frames 100 is bent again outward in the vehicle width direction at the rear end portion 105a of the inclined portion 105. The suspension arm support portions 101 extending from the inclined portions 105 become parallel to each other. A distance between the left and right suspension arm support portions 101 is narrower compared to the central portions 103.
In vehicle body frames 100 constructed in this way, if the entire frame is made shorter, a distance between the two bent positions 103a and 105a, that is, the length of the inclined portion 105, must also be shortened. Together with shortening of the inclined portion 105, in order to make a distance between the left and right suspension arm support portions 101 be narrow and parallel in manner similar to that described above, it becomes necessary to bend each of the vehicle body frames 100 sharply at the two bent portions 103a and 105a. However, processing the frame in this manner is difficult.